ER Model and Business Rules Questions and Answers

Q: A supertype is an entity type that shares common attributes or relationships distinct from other subgroupings.

Correct answer: FalseThat is the definition of a subtype - a subgrouping sharing attributes or relationships distinct from the other subgroupings. A supertype is the general entity type whose attributes and relationships are shared by all of them. The statement has given one definition under the other name.

Q: Which one of the following symbols is not used in an ERD?

Correct answer: CircleThe three shapes of the basic notation are the rectangle for an entity, the oval for an attribute and the diamond for a relationship. Optionality and cardinality are shown by marks on the relationship lines - crow’s feet and strokes - rather than by a shape, so no circle appears.

Q: An action assertion must include which of the following?

Correct answer: All of the above.An action assertion constrains behaviour, and to do so it must name what is constrained, what the constraint is, and what it is constrained against - the anchor object, the action, and the corresponding object. Omit any one and the rule cannot be enforced because something essential is left unstated.

Q: A supertype can only have only one subtype.

Correct answer: FalseA supertype ordinarily has several subtypes, since the point of the construct is to distinguish kinds. A single subtype is possible but unusual and generally means the modeller has found an exception rather than a genuine classification.

Q: An entity instance of a subtype represents the same entity instance of a supertype.

Correct answer: TrueThe supertype and the subtype are two views of one thing, not two things. An instance of the subtype is the corresponding supertype instance, which is what makes attribute inheritance meaningful and why the relationship carries no cardinality.

31.

A supertype is an entity type that shares common attributes or relationships distinct from other subgroupings.

A.True
B.False

Answer: B

Correct answer: False

That is the definition of a subtype - a subgrouping sharing attributes or relationships distinct from the other subgroupings. A supertype is the general entity type whose attributes and relationships are shared by all of them. The statement has given one definition under the other name.

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32.

Which one of the following symbols is not used in an ERD?

A.Rectangle
B.Oval
C.Diamond
D.Circle

Answer: D

Correct answer: Circle

The three shapes of the basic notation are the rectangle for an entity, the oval for an attribute and the diamond for a relationship. Optionality and cardinality are shown by marks on the relationship lines - crow’s feet and strokes - rather than by a shape, so no circle appears.

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33.

An action assertion must include which of the following?

A.Anchor object
B.Action
C.Corresponding object
D.All of the above.

Answer: D

Correct answer: All of the above.

An action assertion constrains behaviour, and to do so it must name what is constrained, what the constraint is, and what it is constrained against - the anchor object, the action, and the corresponding object. Omit any one and the rule cannot be enforced because something essential is left unstated.

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34.

A supertype can only have only one subtype.

A.True
B.False

Answer: B

Correct answer: False

A supertype ordinarily has several subtypes, since the point of the construct is to distinguish kinds. A single subtype is possible but unusual and generally means the modeller has found an exception rather than a genuine classification.

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35.

An entity instance of a subtype represents the same entity instance of a supertype.

A.True
B.False

Answer: A

Correct answer: True

The supertype and the subtype are two views of one thing, not two things. An instance of the subtype is the corresponding supertype instance, which is what makes attribute inheritance meaningful and why the relationship carries no cardinality.

Discuss in Forum

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